Hypoxic tissue exists in most of the solid tumors and hypoxia is a common character of these tumors. The existence of hy-poxic tissue in the tumor decreases the efficacy of radiotherapy and chemotherapy. Radiolabeled hypoxia markers have been developed to measure the hypoxic tissue together with non-invasive imaging techniques such as PET, SPECT, and PET/CT. This offers a conven-ient approach to delineate the tumor providing useful information for diagnosing cancer and guiding the treatment plan. Bioreducible or-ganic compounds have been developed as the hypoxia markers to probe tissue hypoxia noninvasively because they can be reduced and metabolized under hypoxic conditions; form adducts with cell components, and thus be trapped in the hypoxic tissue. These compounds include nitroimidazoles and other redox-sensitive compounds such as BnAO and ATSM. Different radionuclides have been used to label these compounds such as technetium-99m, iodine-123, fluorine-18, copper-64, etc. In addition, to detect h ypoxia with endogenous hy-poxia markers such as carbonic anhydrase IX (CA IX) and hypoxia-inducible factor-1 (HIF-1), some radiolabeled tracers have also been developed. This article is an overview of the progress in this area in the past decade including the development of radiolabeled com-pounds for hypoxia detection and problems associated with the hypoxia marker development.
Keywords: Radionuclide, tumor, hypoxia imaging agent, nitroimidazole, redox-sensitive compounds, radiotherapy, chemotherapy, technetium-99m, iodine-123, fluorine-18
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